1. Field of the Invention
The present invention relates generally to the field of audio fidelity, and more particularly to a vibration isolator such as a microphone isolation system.
2. Background of the Invention
The bandwidth capacity of telecommunications networks is expanding rapidly. This expansion has allowed commercially valuable services such as videoconferencing and voice-over-Internet conferencing to become viable and be technology growth areas. These services may be enhanced with wideband telephony capabilities for enhanced audio fidelity. Of course, terminals that support these services at user locations should be designed to produce and capture wideband voice signals from users. Traditional telephony, still prominent today and spanning from approximately 200 or 300 Hertz (Hz) through approximately 3500 Hz, has existed for over a century. A contemporary wideband telephony service and terminal spans, as an example, 50–7000 Hz or 80–14 kiloHertz (kHz).
There are various drawbacks to the prior art telephony approaches. For example, when one attempts to design a terminal's speech transducers (namely, the microphone and receiver in a handset or the microphone and loudspeaker in a hands-free “speakerphone” terminal) to exhibit wideband response, many acoustical and mechanical difficulties manifest themselves.
One problem that surfaces is that the microphone is exposed to the terminal's solid borne vibrations (e.g., vibrations resulting from a table, the terminal's fan or other moving part, or the terminal's loudspeaker voice coil motion) over a much broader frequency range than otherwise experienced. This problem is particularly troublesome at lower frequencies since mass or inertia of the terminal is not very effective at attenuating such solid borne vibrations before the terminal's microphone senses the vibrations. Virtually all microphones in use today are of an electret type. In spite of the electret microphones' light diaphragms, those diaphragms will still undergo a relative motion with respect to an electret's vibrating metal outer housing, which is normally attached to the terminal in a substantially rigid manner. This relative motion causes a mechanical noise signal to be produced, thus corrupting the terminal's transmission signal.
It is noteworthy that in traditional telecommunications products, electret microphones are typically housed in a rubber “boot” assembly prior to assembly into a terminal. This type of housing is used for acoustical sealing and provides no substantial vibration isolation.
One prior art attempt at isolating vibrations is shown in J. Audio Eng're Soc., February 1971, “Microphone Accessory Shock Mount for Stand or Boom Use,” by G. W. Plice, and depicts a “new isolation mount.” The reference shows a rubber shaped structure looking like a “donut” holding a central microphone load. A continuous annular plate supports the rubber “donut.” The “donut” is curved and thus flexible in a direction normal to a bisecting horizontal plane of the load.
Referring to FIG. 1, another prior art attempt is found within the Panasonic PV-MK40 Camcorder. This camcorder exhibits a “second-order microphone structure” wherein an electret microphone is supported by a central annular rubber platform 100 with circumferentially staggered radial beam supports 102. Some of the beam supports 102 are affixed to a ring 104. The ring 104 is affixed to a wall 106 by other beam supports 108.
In another prior art attempt, shown and described in U.S. Pat. No. 5,739,481 to Baumhauer, Jr. et al., a loudspeaker mounting arrangement uses a compliant member to support and isolate a central loudspeaker load.
Although these prior art attempts may provide some level of isolation from vibrations, the vibration isolation can be improved. Therefore, there is a need for a system and method for providing improved vibration isolation.